Adaptor Signatures for ECC Schnorr

[qubits4all]

Support generation of adaptor ECC Schnorr pre-signatures (a.k.a. verifiable encrypted signatures), verification of such pre-signatures, adapting pre-signatures into full ECC Schnorr signatures, and extracting the private tweak key form a pre-signature and associated full ECC Schnorr signature.

Provide the following functionality:

• Generation of public/private tweak key pairs & ECC Schnorr public/private key pairs.
• Construction of adaptor pre-signatures for ECC Schnorr.
• The pVerify(...) function, which verifies a pre-signature given the public key, public adaptor tweak key, and the message that was signed.
• The Adapt(...) function, which converts an adaptor "pre-signature" into a full ECC Schnorr signature.
• The Extract(...) function, which extracts the private adaptor tweak, given a pre-signature and associated full ECC Schnorr signature.